The usual method to simulate vertical vibrations generated by road transport in laboratory is to use the average power spectral density. With this method, the distribution of the acceleration levels throughout the test is a Gaussian which does not conform to the reality of a transport. This study proposes an improvement of the classical method; this improvement permits to simulate the power spectral density and the distribution of acceleration levels by using a conventional device. The main idea of this method is to decompose the distribution of an actual road transport by using a sum of weighted Gaussians. Then, we apply the power spectral density with the root mean square acceleration (grms) level and duration corresponding to each Gaussian calculated from the weighted sum. We show that the weighting coefficients correspond to the time fraction of the test. Over the total duration of the test, we then retrieve the acceleration levels distribution of the actual transport. This new test method is experimentally validated with 2 examples of actual transports.
Vibrations and shocks are found among mechanical phenomena undergone by packaging systems. In order to verify the behaviour of packaging systems under shocks, test protocols advocate the execution of drop tests, inclined plane tests, forklift handling courses and so on in laboratories. Nevertheless, even if these protocols are efficient, they do not replicate the wide variety of transient events occurring during transportation. That is why there is a need in developing a method capable of replicating actual transient events in a reproductive way in laboratories. This work concerns the comparison of the responses of a packaging system subjected to two different simulations of the same transient event with the aim to forward develop specifications. The definition and elaboration of shock response spectra (SRS) are reviewed in the first part of this work. Afterwards, a data acquisition enables the recording of classical transient events generated by a forklift. Then the calculation of the SRS of one of those transient events enables the generation of a time signal different from the transient event recorded. Finally, a comparison between the response of a packaging system subjected to the time transient event as it is recorded and the response to the time transient event calculated from the SRS is carried out. The first results based on the study of autocorrelation functions, intercorrelation functions, energy spectral densities (ESDs) and damage calculation conclude towards an equivalence between a real‐time replication and an SRS simulation in the case of one transient event and one packaging system.
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